Epidural steroid injections (ESIs) are used frequently for a variety of back conditions and are considered to be safe procedures. However, several case reports have shown that even a single dose of ESI can cause adrenal suppression. This study was designed to determine whether a single epidural injection with corticosteroids plus lidocaine causes greater cortisol suppression than does an epidural injection with lidocaine alone.

Subjects were 400 patients with low back pain who were scheduled for an ESI. The participants were randomized to receive an epidural with corticosteroid plus lidocaine (CL) or lidocaine alone (L). A morning fasting serum cortisol level was measured at baseline and again three weeks after the epidural.

Overall, patients in the CL group averaged a 14.4% reduction in cortisol at week three as compared to baseline, while the L group had an average increase of 8.2%. Of the four different corticosteroids used, those injected with methylprednisolone or triamcinolone had reductions in cortisol at three weeks of 41% and 41.6%, respectively (P＝0.005 and P<0.001, respectively). Those treated with betamethasone or dexamethasone had an average cortisol reduction of 1.8% and 23.3%, respectively.

This study confirms that a single epidural steroid injection can suppress cortisol levels for up to three weeks after the injection.